code: def test_unable_to_substitute(self):
      texts = [
          "Insomnia, sleep apnea diagnoses up sharply in U.S. Army."
      ]
  
      for aug in self.augs:
          for text in texts:
              augmented_data = aug.augment(text)
              augmented_text = augmented_data[0]
              self.assertEqual(text, augmented_text)
  
file_path: nlpaug/test/augmenter/word/test_antonym.py
imports: import unittest
  import os
  from dotenv import load_dotenv
  import nlpaug.augmenter.word
label_desc: Use image node_id 3 for calling the TestAntonym obj's underlying member method code with example usage: obj.test_unable_to_substitute() without return types